1. Field of the Invention
The invention relates to a displacement detector of a shock absorption unit for a treadmill, and more particularly, to a device utilizing optical detection technique to accurately measure the displacement amount of the shock absorption unit when a force is applied onto a platform of the treadmill. Accordingly, a corresponding cushioning force of the shock absorption unit can be precisely controlled.
2. Description of the Related Art
In general, the treadmill is provided with cushioning apparatuses at suitable places for achieving a proper cushioning effect and enhancing the comfort of the operator during a workout session. Meanwhile, a protection mechanism has been developed for preventing both feet of the operator from being injured due to the too large reactive force of the platform of the treadmill. It will be particularly beneficial to the operator if hydraulic or pneumatic cylinders are used to provide more excellent cushioning effect. A few prior arts such as U.S. Pat. Nos. 4,591,147, 5,184,988, 4,974,831, 4,984,810, 5,072,928, 5,372,559, etc. have disclosed the application of hydraulic or pneumatic cylinders to the treadmill.
Although the above-mentioned prior arts have advantages of more excellent protection effect and greater comfort, they all don""t have any automatic mechanism for adjusting the cushioning force by operators themselves to meet their own different requirements. In brief, an operator with heavier weight would feel that the cushioning force is too slight while an operator with lighter weight could feel that it is too strong if the cushioning force is fixed at a certain extent. Besides, different operators are their own subjective feeling about the cushioning strength no matter how strong or light the cushioning force is. In addition, some operators have special rehabilitation requirements thereto. Accordingly, the prior arts are required for improvement.
It is a primary object of the present invention to remove the above-mentioned drawbacks and to provide a shock absorption structure for a treadmill that employs hydraulic or pneumatic cylinders as shock absorption source. The cushioning apparatus is adjustable. Meanwhile, the present invention utilizes optical detection technique to accurately measure the displacement amount of the shock absorption unit when an operator stands on a platform of the treadmill. Accordingly, a corresponding cushioning force of the shock absorption unit can be precisely controlled.